In recent years, with the spread of computers, ink jet printers have been widely used to print on paper, film, cloth, etc. at offices as well as at home.
Examples of ink jet recording method include a method which allows a piezoelectric element to give pressure that causes a droplet to be ejected, a method which comprises heating the ink to generate bubbles, causing a droplet to be ejected, a method involving the use of ultrasonic wave, and a method which uses electrostatic force to suck and discharge a droplet. As inks for these ink jet recording methods there are used aqueous inks, oil-based inks and solid (melt type) inks. Among these inks, aqueous inks are mainly used from the standpoint of producibility, handleability, odor, safety, etc.
The dyes to be incorporated in these inks for ink jet recording are required to exhibit a high solubility in solvents, allow a high density recording and have a good hue and an excellent fastness to light, heat, air, water and chemical, a good fixability to image-receiving materials, difficulty in running, an excellent preservability, no toxicity and a high purity and be available at a low cost. However, it is extremely difficult to seek coloring agents meeting these requirements to a high extent. In particular, dyes having a good magenta hue and an excellent light fastness have been keenly desired.
Various dyes and pigments have been already proposed for ink jet recording and have been actually used. However, no coloring agents meeting all these requirements have been found yet. Known dyes and pigments provided with color index (C.I.) can difficultly satisfy both the hue and fastness requirements for inks for ink jet recording. As dyes capable of enhancing fastness there have been proposed azo dyes derived from aromatic amines and 5-membered heterocyclic amines in JP-A-55-161856. However, these dyes are disadvantageous in that they have an undesirable hue in yellow and cyan ranges, causing deterioration of color reproducibility. JP-A-61-36362 and JP-A-2-212566 disclose inks for ink jet recording intended to meet both the requirements for hue and light-fastness. However, the dye stuffs used in the above cited patents exhibit an insufficient water solubility when used as water-soluble inks. These dyestuffs are also disadvantageous in that when used as water-soluble inks for ink jet recording, they also cause problems of wet heat fastness. As means for solution to these problems there have been proposed compounds and ink compositions in JP-T-11-504958. Further, inks for ink jet recording which comprise pyrazoloaniline azo incorporated therein to improve hue or light-fastness are disclosed in Japanese Patent Application No. 2000-80733. However, these inks for ink jet recording have been found disadvantageous in that they can cause image deterioration under severe conditions such as prolonged storage at high temperatures or in the presence of gas such as nitrogen oxide and ozone. In order to eliminate these difficulties, the kind of dyes to be used have been studied. For secondary colors such as blue or gray, however, the effect of enhancing fastness cannot be sufficiently observed due to ill-balanced hues merely by changing one dye. Further, the mixing of two dyes causes interaction that can further deteriorate fastness. It has thus been desired to provide an ink set, cartridge and printer capable of remarkably enhancing fastness to give a high fastness image.